1. Field of the Invention
This invention relates to a vane controller for controlling a plurality of vanes disposed in a fluid conduit and more particularly, to a vane controller for driving a set of vanes which effect capacity control in a fluid machine such as a turbo-compressor having a vane wheel such as, for example an axial or radial flow vane wheel.
2. Description of the Prior Art
A conventional vane control apparatus is disclosed, for example, in Japanese Patent Publication JP-B-57-49759 includes, as shown in FIGS. . This apparatus will be explained with 9 to 11, a vane wheel 1 of a centrifugal compressor and a casing 2 for the flow control vanes and the vane controller attached to a suction bell mouth 2a. A plurality of vanes 3 are mounted upstream of the vane wheel 1, with one of vane 3 being a driving vane 3a. The outer end portions of these vanes 3, 3a are supported by vane shafts 4, 4a carried by ball bearings 5 disposed in the casing 2. A driving arm 6 is fixed to the driving vane shaft 4a and a connecting rod 7 has one end fitted to the driving arm 6 by a pin 8 and the other end fitted to an actuator 9. The driving vane shaft 4a is rotated by the operation of the actuator 9.
A driving control lever 10 is fitted at one end to the driving vane shaft 4a and the other end of this lever 10 is connected to a control ring 11, which is arranged to slidably rotate around the outer periphery of the casing 2 adjacent to the vane shafts 4, 4a, through a linkage 12 composed of two universal joints. Since each vane shaft 4 is connected to the control ring 11 through a follower control arm 14 with a similar linkage 13, all the vane shafts 4 are rotated in synchronism with the driving vane shaft 4a through the control ring 11 when the driving vane shaft 4a is rotated by the operation of the actuator 9. Thus, the degree of opening of the vanes is selected.
A problem with this conventional vane control mechanism is as follows resides in the fact that the control ring 11 moves round the surface of the casing 2 and frictional resistance is great so that the torque required of the actuator for driving all the vanes 3 is considerable. If this frictional torque can be reduced, the torque required is only the air torque acting on each vane 3, 3a and consequently, the torque necessary for moving the vanes can be reduced drastically. Large frictional resistance results in poor response of the vane opening and closing operation and is not suitable for the case where the vanes are repeatedly opened and closed. In addition, the linkage between the levers and the control ring is complicated.
Japanese Utility Model Publication JP-B-44-21729 discloses another vane control mechanism applied to rotating vanes in an axial compressor, in which a control ring in a fixed axial position moves the vane shafts through levers having spherical ends received in bearing sleeves which slide both radially and axially in apertures in the control ring. The ring is spaced from the compressor duct wall and slides at its inside face on the projecting ends of the vane shafts. A disadvantage of the vane control mechanism of the last-mentioned type resides in the fact that the rotating lever is difficult to machine thereby causing high production costs since spherical machining is necessary for the spherical bearing and the tip of the lever.